/Engine/Source/Runtime/RenderCore/Public/RenderGraphBuilder.h
Configures the resource for external access for all subsequent passes, or until UseInternalAccessMode is called. Only read-only access states are allowed. When in external access mode, it is safe to access the underlying RHI resource directly in later RDG passes. This method is only allowed for registered or externally converted resources. The method effectively guarantees that RDG will transition the resource into the desired state for all subsequent passes so long as the resource remains externally accessible.
void UseExternalAccessMode ( [FRDGViewableResource](API\Runtime\RenderCore\FRDGViewableResource) * Resource, ERHIAccess ReadOnlyAccess, ERHIPipeline Pipelines )